it's pretty bad. >> we are live on the scene. videos still coming in with the breaking details. the catastrophe in texas. >> announcer: from abc news, live in times square, thursday april 18th, 2013. this is "good morning america." with robin roberts and george stephanopoulos. >> and good morning, america. details streaming in all night on the devastating explosion at a fertilizer plant in texas. this stunning photo tells the terrifying story. there you see it, the kind of mushroom cloud created by a nuclear bomb. >> in fact, this is what it looked like and sounded like as it happened. >> it had the force of a small earthquake registered on the seismograph more than 400 miles away in amarillo, texas, and more concerns whether ammonia from the plant was released into the air, how far it could spread. dr. besser has been tracking that part of the story.